1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device and more particularly, to a liquid crystal display (LCD) device having a multi-domain structure for improving a viewing angle.
2. Discussion of the Related Art
In general, a liquid crystal display (LCD) device utilizes an optical anisotropy and birefringence properties of liquid crystal molecules to display images. The liquid crystal display (LCD) device usually has first and second substrates spaced apart from and opposing each other. The first and second substrates respectively have electrodes for forming an electric field between the electrodes. That is, if voltage is applied to the electrodes of the liquid crystal display (LCD) device, an electric field is formed between the electrodes and the electric field changes alignments of the liquid crystal molecules. The changed alignments of the liquid crystal molecules control a light transmittance through the liquid crystal and thus images can be displayed by controlling the light transmittance through the liquid crystal.
FIG. 1 is an exploded perspective view of a related art liquid crystal display (LCD) device. In FIG. 1, a liquid crystal display (LCD) device 11 has an upper substrate 5 having a color filter 7 and a common electrode 18 on the color filter 7, and a lower substrate 22 having a thin film transistor “T” and a pixel electrode 17 connected to the thin film transistor “T”. The color filter 7 has sub-color filters 8 and a black matrix 6 formed between sub-color filters 8. A plurality of pixel regions “P” is defined on the lower substrate 22 and array lines are formed around the pixel region “P”. Liquid crystal 14 is interposed between the upper and lower substrates 5 and 22. A gate line 13 is formed in a first direction. A data line 15 is formed in a second direction perpendicular to the first direction. The gate and data lines 13 and 15 define the pixel region “P” by crossing each other, and the thin film transistor “T” is formed near a crossing portion of the gate and data lines 13 and 15. The thin film transistors “T” are formed in a matrix form on the lower substrate 22, i.e., an array substrate. The pixel electrode 17 is formed of transparent conductive metal material such as indium tin oxide (ITO) in the pixel region “P”. A storage capacitor C connected to the pixel electrode 17 in parallel is formed over the gate line 13. A portion of the gate line 13 serves as a first storage electrode and a source-drain metal layer formed of same material as source and drain electrodes on a same layer as the source and drain electrodes serves as a second storage electrode. The source-drain metal layer contacts the pixel electrode 17 to receive a signal from the pixel electrode 17. Because liquid crystal molecules align by an electric field formed between the common and pixel electrodes 18 and 17, the liquid crystal display (LCD) device (specifically TN (twisted nematic) mode liquid crystal display (LCD) device) has a poor viewing angle. To overcome the aforementioned problem, a method to improve a viewing angle by dividing the pixel region into many domains where the liquid crystal molecules in one of the domains have a symmetric orientation to the orientation of the liquid crystal molecules in a next domain, has been suggested. A structure of the liquid crystal display (LCD) device to improve the viewing angle will be described hereinafter with reference to FIG. 2 and FIG. 3.
FIG. 2 is a plan view of a related art liquid crystal display (LCD) device having a multi-domain structure, and FIG. 3 is a cross-sectional view taken along a line “III—III” in FIG. 2. In FIG. 2 and FIG. 3, a first substrate 50 and a second substrate 70 opposing the first substrate 50 are spaced apart from each other. Gate and data lines 52 and 54 defining a pixel region “P” by crossing each other are formed on the first substrate 50, and a thin film transistor “T” having a gate electrode 56, an active layer 58, a source electrode 60 and a drain electrode 62 are formed near a crossing portion of the gate and data lines 52 and 54. A pixel electrode 64 connected to the drain electrode 62 is formed in the pixel region “P”, and a side electrode 66 encompassing the pixel electrode 64 is formed around the pixel electrode 64. A black matrix 72 corresponding to the thin film transistor “T”, the gate line 52, the data line 54 and the side electrode 66 is formed on the second substrate 70. A color filter having sub-color filters 74a, 74b and 74c respectively for red (R), green (G) and blue (B) colors is formed on the second substrate 70 and covers the black matrix 72. A common electrode 76 is formed on the color filter, and an organic layer pattern 78 having a certain width is formed on the common electrode 76 in a same direction as the gate line 52. The organic layer pattern 78 and the side electrode 66 serves to form a fringe field for forming an abnormal electric field between the common and pixel electrodes 76 and 64. The organic layer pattern 78 divides the pixel region “P” into a first domain “A” and a second domain “B”. Accordingly, because liquid crystal molecules 80 in the first domain “A” has a different alignment direction from the liquid crystal molecules in the second domain “B”, it is not required to perform a rubbing process twice to form a multi-domain in the pixel region “P”. However, because the side electrode 66 is formed of the same material as the pixel electrode 64 on a same layer as the pixel electrode 64, a short between the side electrode 66 and the pixel electrode 64 may happen when there is an error during forming process of the side electrode 66 and the pixel electrode 64. Accordingly, to overcome the aforementioned problem, an appropriate interval must be provided between the side electrode 66 and the pixel electrode 64. However, as the interval between the side electrode 66 and the pixel electrode 64 increases, an aperture ratio is greatly reduced.
In addition, the liquid crystal display (LCD) device having a multi-domain structure can be more stably driven as the number of divided domains in the pixel region increases. However, because many slit patterns must be used to divide the pixel region into many domains, the aperture ratio may be decreased greatly.